Risk factors and treatment outcome of bloodstream infections caused by Pseudomonas aeruginosa isolates producing the PER-1 extended-spectrum b-lactamase
Abstract number: o75
Endimiani A., Pini B., Luzzaro F., Amicosante G., Rossolini G.M., Toniolo A.
Clinical significance of bloodstream infection (BSI) due to Pseudomonas aeruginosa (Pa) has received large attention. In contrast, the clinical impact of BSI caused by ESBL-positive isolates has not been investigated. The PER-1 ESBL is a common enzyme conferring high-level resistance to anti-pseudomonal cephalosporins. This study was initiated to evaluate risk factors and treatment outcome of BSI episodes caused by PER-1-positive Pa strains (PER-1-P-Pa).
From January 1998 to September 2004, 26 BSI cases due to ceftazidime-resistant Pa strains were observed at the Ospedale di Circolo, Varese, Italy. MIC values of anti-pseudomonal drugs were determined by the E-test method (AB Biodisk, Solna, Sweden). The double-disk synergy test was used to detect ESBL production. Molecular methods (PCR amplification and DNA sequencing) were used to characterize ESBL types. Clinical records of BSI-patients were examined retrospectively. Demographic data, underlying diseases (according to McCabe-Jackson classification and Charlson weighted index), risk factors, antimicrobial therapy, and treatment outcome were investigated by comparing cases due to ESBL-positive to those due to ESBL-negative Pa isolates. Unpaired Student's t-test, Mann-Whitney U-test, and Chi-square were used for statistical analysis.
Nine Pa isolates were found to express the PER-1 ESBL whereas the remaining 17 were PER-1-negative (PER-1-N-Pa). Severe sepsis (P = 0.03), bladder and intravascular catheters (both, P = 0.01), immunosuppressive therapy (P = 0.04), and mechanical ventilation (P = 0.03) were significantly associated with BSI due to PER-1-P-Pa. Empirical treatment (P = 0.02) and treatment after ID/AST (P < 0.01) were less adequate in PER-1-P-Pa cases. Hospital admission and longer mean length of hospital stay after BSI onset (P = 0.07 and P = 0.08, respectively) was possibly related to expression of the PER-1 enzyme. Overall, 77.8% BSI cases due to PER-1-P-Pa vs. 28.6% cases due to PER-1-N-Pa isolates failed to respond (P < 0.03). Notably, all cases due to PER-1-P-Pa that were treated with carbapenems failed to respond. In contrast, 7/8 cases due to PER-1-N-Pa given carbapenems were responders.
Therapeutic failure and poor outcome are associated with BSI episodes caused by PER-1-P-Pa strains. Thus, recognition and prompt reporting of ESBL-production appears a critical factor for the management of patients with serious P. aeruginosa infections.
|Session name:||XXIst ISTH Congress|
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